Unintended deformation of semiconductor devices may be a well-known problem in the semiconductor industry. This problem has been addressed by inspecting semiconductor devices and components both before (pre-seal) and after (post-seal) the devices or components are packaged for shipping. Existing methods for performing post seal inspection require the use of an operator to perform 100 percent inspection, because of variability in the sealing tape used for immobilizing semiconductor devices and components.
The current process used by most manufacturers is to do an automated vision inspection at pre-seal and a post seal gross manual inspection. The post seal gross manual inspection involves examining the devices with the human eye through a magnifying glass. Although doing a manual post seal inspection is better than doing no post seal inspection at all, the manual post seal inspection is very time consuming and not very cost effective and therefore not very efficient. In addition, as more and more semiconductor processes become automated, a manual post seal inspection becomes less desirable.
No automated method has been developed that can examine the semiconductor devices for defects after the devices have packaged for shipping. The problem has been the ability to generate a clear and detailed image of the semiconductor device when such device is disposed beneath a layer of sealing or cover tape. The sealing or cover tape layer causes extreme light scattering and light reflection, which can severely distort the image of the device beneath the tape. Because of this image distortion caused by the sealing or cover tape layer, the practice in the field has been to merely do a manual post seal inspection of devices packaged under sealing or cover tape.
Although it is desirable to automate all inspection processes for semiconductor devices and components, many physical obstacles have prevented an automated post seal inspection system for devices and components disposed beneath the sealing or cover tape. The glossy cover tape causes light reflection and light dispersion, which creates noise when a camera is trying to produce an image of the device. The cover tape is not very translucent so the clarity of the device disposed beneath the tape is impaired. Also, the cover or sealing tape has anti-static coating as well as filler particles that worsen visibility through the cover or sealing tape. Finally, the inside and outside surfaces of the cover or sealing tape are not perfectly parallel which creates a prism and cause the device disposed beneath to appear distorted.